Plastic cards in the general shape and size of credit cards, but with embedded integrated circuit chips are well known in the art. Such devices have appeared as articles of commerce in numerous applications where low cost electronic devices for personal use are required, such as bank cards, phone cards and the like. They are known as smart cards or IC cards. There was no teaching in the prior art concerning the use of card systems of this type that have been modified by removal of the integrated circuit chip and addition of fluidic and sensor elements for use in chemical analysis or in-vitro diagnostics, prior to the following published disclosures which are related to this invention. Electrode Module U.S. Pat. Publ. No. US 2002/017944 A1, Point-of-Care In-Vitro Blood Analysis System U.S. Pat. Publ. No. US 2003/0148530 A1, both of which are incorporated herein by reference.
In the co-pending and related patent application entitled Heterogeneous Membrane Electrodes, U.S. patent application Ser. No. 10/307,481 there is disclosed a diagnostic card containing a sensor array on an electrode module comprising a heterogeneous membrane reference electrode and electrochemical indicator electrodes, the disclosed electrode module being contained in a credit card sized fluidic housing. This present patent application now discloses additional inventive components and inventive elements of an electrode module and a diagnostic card incorporating fluidic elements.
Diagnostic test cards and cartridges for chemical analysis are well known in the art. Diagnostic cards and cartridges incorporating sensors and fluidic elements are known in the art. Early examples are U.S. Pat. No. 4,301,412 that discloses a pair of electrodes in a plastic housing with an orifice for sample introduction and a capillary conduit for sample flow to the electrodes. Similar devices were also disclosed in the capillary flow technology described in U.S. Pat. No. 5,141,868. Diagnostic card devices with sensors and fluidics also incorporating on-board fluids contained in sealed housings within the cartridge were disclosed in U.S. Pat. Nos. 4,436,610 and 4,654,127. The '127 device consisted of a plastic card-like housing with sensors and conduits with a sealed chamber containing a calibrating fluid mounted on the card. In use of this device the seal of the fluid-containing chamber was ruptured when the user manually turned a chamber element and subsequent fluid propulsion to the sensors on the card was by gravity. An improved diagnostic cartridge with sensors, fluid conduits and on-board fluid was disclosed in U.S. Pat. No. 5,096,669. This device consisted of a sensor array on a microfabricated silicon chip in a plastic housing with fluidic conduits, as well as a sealed pouch containing a calibrating fluid. The improvement was that the device was designed so that the fluid containing pouch could be ruptured and calibrating fluid moved to the sensors by the read-out instrument rather than manually. In the use of this device the sample is collected into the card away from the sensors, then subsequently moved to the sensor location by an instrument means. In both the '127 and '669 patents the fluid seal is made by a foil coated element and its rupture is by a piercing element that rips through the foil. U.S. Pat. No. 5,325,853 discloses a diagnostic device with sensors and fluidics with on-board fluid that is not sealed remotely from the sensors.
Of the devices of the prior art only the '669 device has proven commercially useful for the measurement of a broad range of analytes in parallel in sensor panels. The '669 device incorporates many unique and proprietary designs and special purpose components. The manufacturing processes also are unique to their devices and specialized assembly equipment is required. The '669 device and other prior art diagnostic devices generally require numerous process steps in electrode manufacture and numerous piece-parts and precision assembly steps in the card manufacture. Thus, this technology has proven expensive to manufacture, thereby limiting the broader utilization of the technology.
There are also performance limitations of the '669 technology. The fluid in the foil-lined and sealed reservoir has very limited shelf stability because the seal lengths are short. Furthermore, the reservoir is pressurized during fabrication and the sealed reservoir is ruptured during use by piercing the foil reservoir under applied pressure. Therefore the fluid in the reservoir is under pressure and, thus, has the potential to be evacuated from the reservoir in an explosive manner causing a potential for segmented fluid flow. Such problems can reduce the reliability of the '669 device. The sample transfer into the sample collection area of the '669 device is not done anaerobically. This may result in errors when measuring dissolved gases such as oxygen and carbon dioxide, particularly in samples which have low buffer capacity for those gases. Furthermore, there is no provision for reliable thermostating of the test fluid adjacent to the sensors.
There is now a need to provide for simpler and more generic designs and manufacturing procedures for sensor arrays and fluidics in diagnostic-card devices.